This invention relates in general to the testing of a producing well, and in particular, relates to the testing of production capacity and quality to ensure the best possible performance of the well, and especially, to allow optimum drainage of the reservoir concerned.
Such tests, in accordance with prior art methods currently used, generally include the plotting of a flow-pressure graph which represents the inflow performance of the well. This graph is obtained by measuring the variations in the pressure of fluids at the bottom of the well over the producing zones when the total production flow is made to vary. In practice, the curve representing these variations is obtained from a small number of points. For example, two or three different production flows, including zero flow, are imposed successively and, for each of these flows measured at the surface, the corresponding pressure is measured at the bottom of the well at a level located over the producing zones.
Thus, the U.S. Pat. No. 2,348,192 (L. S. Chambers) proposes the downhole measurement of the pressure and the flow at several points of the interval covering the production zones. By combining the flow and pressure measurements, the technique described in the Chambers patent makes it possible to obtain performance curves by production zone, each curve indicating the variations in flow of each zone as a function of the variations in pressure at a selected depth of the well.
One of the difficulties of the Chambers technique lies in the pressure measurements, which must be very precise and taken at very precise depths. A pressure profile is difficult to obtain continuously along an interval of the well because of the usual defects of sensors which are generally subjected to temperature drifts or require significant time constants for the measurement. Consequently, the pressure measurements for which a good accuracy is required must be carried out in a stationary manner. The physical measurement of the pressure is not always possible at the desired level, for example at the top of effective production zones, the exact locations of which are not known before the logging operation. Moreover, it is difficult to come back exactly on several occasions to the same level when one wishes to carry out several successive pressure measurements at the same depth of the well.
It is the object of this invention to provide a well pressure profile in a precise manner, in particular where precise measurements for the testing of a production well are desired.
More generally, the object of the invention is to provide a method for testing a producing well making it possible to plot good performance curves per zone through the obtaining of adequate pressure data.